The specific aims of this study will be to determine if individuals at risk for developing Type II diabetes mellitus (DM) have insulin resistance of glucose transport and phosphorylation within skeletal muscle using positron emission tomography (PET). Secondly, to determine if a) obese offspring of parents with type 2 diabetes mellitus (DM) have impairments in glucose transport and/or phosphorylation and b) if weight loss can improve glucose transport and phosphorylation. Three groups of subjects will be studied: 1) obese subjects with Type II DM, 2) obese subjects with a family history of Type II DM and normal glucose tolerance, and 3) obese subjects with no family history of Type II DM and normal glucose tolerance. This study will test the hypothesis that weight loss improves both glucose transport and phosphorylation, and that the effect of weight loss on these parameters is similar across the three groups.